Before Christmas, I worked on a project which involved scanning and transcribing the letters of a WWII soldier (Grandpa B) to his wife (Grandma B). It was a really fun project and gave me a nice break from unpacking and remodeling. J helped me transcribe some letters, including one that discussed Grandpa B's reaction to Roosevelt's sudden death. Both J and I knew that Roosevelt had died suddenly, but neither of us knew the details.
After looking it up, we discovered that Roosevelt collapsed on April 12, 1945 while he was sitting for a portrait with the painter Elizabeth Shoumatoff. He died that same day from a cerebral hemorrhage. I don't think there are any other important historical figures who have collapsed (and subsequently died) while sitting for a portrait. (Can anyone prove me wrong?)
This is a reproduction of Shoumatoff's unfinished portrait of the president. The original portrait hangs in "The Little White House" museum in Georgia.
As has been commented elsewhere, I think that that this unfinished portrait is a visual representation of FDR's unfinished presidential term. Roosevelt never got to see the defeat of Nazi Germany (V-E Day), and although he ordered the construction of the atomic bomb, he never was faced with the decision of dropping it on Japan. Truman had to pick up and finish Roosevelt's incomplete work. Legal scholar Cass Sunstein argues that Roosevelt's political work is still left unfinished; in 2004 Sunstein published The Second Bill of Rights: FDR's Unfinished Revolution and Why We Need It More than Ever.
In 1991 Shoumatoff published a memoir regarding her experience of painting "The Unfinished Portrait." I plan on reading it soon.
I also found online a transcript of Robert G. Nixon's oral history. He also has some interesting recollections of the day FDR died.